You should apologise for things that you have done, that you recognise that perhaps you shouldn't have done or regret. But apologising for things that your great, great, great, great-grandfather or grandmother did, seems to me a complete exercise in moral vacuousness.

It is certainly true that Blair came close to apologising for slavery. In an article for the New Nation in 2006, on the bicentenary of the abolition of slavery, the former prime minister expressed his "deep sorrow" for Britain's role in the slave trade.

But on the Irish potato famine Paxman is wrong on two counts:

• Blair was careful not to apologise for the potato famine in his landmark declaration in 1997 to a concert marking the 150th anniversary of the famine. This is what the newly elected prime minister said in a statement read out to the concert in Co Cork by the actor Gabriel Byrne:

The famine was a defining event in the history of Ireland and of Britain. It has left deep scars. That one million people should have died in what was then part of the richest and most powerful nation in the world is something that still causes pain as we reflect on it today.

Those who governed in London at the time failed their people through standing by while a crop failure turned into a massive human tragedy. We must not forget such a dreadful event.

• Blair's intervention was not a sign of "moral vacuousness", as Paxman says in the Radio Times. It was a highly calculated move to show to nationalist Ireland that he was leading a very modern British government that was keen to deal with Ireland, north and south, in an even-handed manner free from the shackles of the past.

This was acknowledged by John Bruton, the Irish prime minister, who told me at the time:

While the statement confronts the past honestly, it does so in a way that heals for the future. The prime minister is to be complimented for the thought and care shown in this statement.

Blair, who spent summer holidays as a child in Co Donegal, had given a great deal of thought before the 1997 election about how to deal with Northern Ireland. The peace process had reached an impasse after John Major was unable to offer Sinn Féin a full seat at negotiations after the IRA's 1994 ceasefire. This had prompted the IRA to end its ceasefire in 1996. It is often forgotten that there was no ceasefire in place when Blair became prime minister.

Blair calculated that he needed to achieve what then seemed impossible: reassure Unionists while making a substantive offer to Sinn Féin. He did this in his first speech in Belfast on 16 May 1997, just over two weeks after his election, when he offered the party the chance to meet government officials even though there was no IRA ceasefire. In the same speech Blair reassured Unionists by saying he thought it was unlikely there would be a united Ireland in his lifetime.

The substance of the Belfast speech was therefore aimed at republicans while the optics were aimed at Unionists. This meant that Blair knew he had more work to do on the optics for republicans. The Co Cork concert two weeks later provided the perfect opportunity.

As a former BBC Belfast correspondent at the height of the Troubles, Paxman will probably say it is absurb to say that a gesture on the famine would impress republicans. It is certainly true that republicans were far more interested in an apology for Bloody Sunday than for the famine.

But Blair, who later established an inquiry into Bloody Sunday, calculated that he needed to show reach out to nationalist Ireland. A gesture on the famine was a small, but important, step in that direction.

Blair's reward came a few weeks later when the IRA restored its ceasefire.